A Micro-Electro-Mechanical System, or MEMS, is a technology that in its most general form can be defined as miniaturized mechanical and electro-mechanical elements (i.e., devices and structures) that are made using the techniques of micro-fabrication. A MEMS microphone element is a microphone made by the MEMS technology. A MEMS microphone element can be first manufactured and then it is encapsulated into a MEMS microphone device on a substrate. The MEMS microphone device can further be assembled into an electronics apparatus such as a mobile phone, a pad, a laptop and so on.
Because of the small size of the MEMS microphone element, the environment of manufacturing will influence the performance of an electronics apparatus which has a MEMS microphone device.
Generally, a MEMS microphone device has an acoustic port to let the sound pressure come into the MEMS microphone element and interact with its diaphragm. Dusts or particles can enter the acoustic port and thus the performance of the MEMS microphone device may be degraded.
In the prior art, some technicians use a filter with mesh holes at the acoustic port to protect the MEMS microphone element. In order to relieve the influence of the dust or particle, technicians try to reduce the size of the mesh holes of the acoustic port or to use a rigid plate filter for the acoustic port. However, this will degrade the performance of the MEMS microphone device, such Signal-Noise-Ratio (SNR).
In addition, due to fabrication process constraints, it is just feasible to fabricate very large mesh holes currently, for example, the sizes of which are about 100 μm or more. By using such a filter, killer particles for a MEMS microphone element of 2˜5 μm, such as PM 2.5 particles, cannot be blocked out efficiently.
Furthermore, the dimension of such a filter will influence the performance of the MEMS microphone device. For example, with the increasing of the thickness of the filter, the SNR may decrease. For example, with the size reduction of the mesh holes of the filter, the SNR may also decrease. For example, with the thickness increase of the filter, the frequency response of the MEMS microphone device may be deviated.
U.S. Pat. No. 9,438,972 B2 discloses a Silicon based MEMS microphone, a system and a package with the same, which is hereby incorporated herein by reference.
U.S. Pat. No. 8,447,057 B2 discloses packages and methods for packaging MEMS microphone devices, which is hereby incorporated herein by reference.
X. Yang, et al, Micromachined membrane particle filters, p. 137-142, Micro Electro Mechanical Systems Conference, February 1998 discloses several particle membrane filters with circular, hexagonal and rectangular through holes, which is hereby incorporated herein by reference.
Therefore, there is a demand in the art that a new solution for a MEMS microphone device shall be proposed to address at least one of the problems in the prior art.